1. Technical Field
The present disclosure relates to a light emitting diode (LED).
2. Discussion of Related Art
LED modules are widely used as light sources in optical imaging systems, such as displays, projectors, and so on.
A conventional LED commonly includes an N-type semiconductor layer, a P-type semiconductor layer, an active layer, a first electrode, and a second electrode. The active layer is located between the N-type semiconductor layer and the P-type semiconductor layer. The second electrode is located on the P-type semiconductor layer. The first electrode is located on the N-type semiconductor layer. Typically, the second electrode is transparent. In operation, a positive voltage and a negative voltage are applied respectively to the P-type semiconductor layer and the N-type semiconductor layer. Thus, the holes in the P-type semiconductor layer and the electrons in the N-type semiconductor layer can enter the active layer and combine with each other to emit visible light.
However, the efficiency of LEDs is limited by several factors including the visible light emitted from sidewalls of the LEDs cannot be used. Therefore, an external quantum efficiency of LEDs is low.
What is needed, therefore, is to provide a light emitting diode, which can overcome the above-described shortcomings.